As we all know, the continuous progress of electronic equipment and circuit technology, the peak of engineering art in the design, development and manufacture of bwrdd cylched printiedig Mae pobl ledled y byd wedi bod yn dyst i (PCB). Our planet is full of highly intelligent machines, automated robots and scientific marvels, and of course, there are plenty of PCBS in every corner of the planet, no matter what country or city it is. Fodd bynnag, mae’r PCBS hyn yn wahanol o ran ymarferoldeb, cymhlethdod, cost cynhyrchu, ansawdd a dibynadwyedd. Mae’r erthygl hon yn canolbwyntio ar y ddau bwynt olaf, ansawdd a dibynadwyedd PCBS.

Ydy, mae darpar gwsmeriaid bob amser eisiau electroneg o ansawdd uchel, ond mae hyn yn ddrud iawn a gall gynnwys prosesau gweithgynhyrchu cymhleth. Yn y broses gymhleth o weithgynhyrchu, cydosod a phrofi PCB, mae yna broses bwysig iawn o’r enw “cotio cydffurfiol” o PCB. Mae’r cotio cydffurfiol hwn yn bwysig iawn yn PCBS o ran ansawdd a dibynadwyedd.

Beth yw cotio cydffurfiol a’i bwysigrwydd:

Conforming coating, an ultra-thin protective coating of polymer film, can be used in conjunction with assemblies mounted on assembly surfaces to protect assembly leads, solder joints, exposed wiring, and other metal points on the PCB surface from corrosion, dust, or chemicals due to various operating or environmental conditions.

Gall y cotio cydffurfiol fod mor denau â 25 micron ac mae’n “cydymffurfio” â siâp a chynllun cydran y bwrdd cylched. Fel y soniwyd uchod, y rheswm dros roi gorchudd cydffurfiol ar wyneb (brig a gwaelod) PCB yw amddiffyn y PCB rhag amodau amgylcheddol allanol niweidiol, a thrwy hynny gynyddu oes gwasanaeth y PCB a’r offer electronig cysylltiedig.

Fel tymereddau uchel a geir mewn electroneg ddiwydiannol, ffatri a phwer uchel, gall y PCBS hyn â haenau cydffurfiol wrthsefyll tymereddau eithafol. Yn yr un modd, gall lleithder uchel effeithio ar offer electronig sydd wedi’i osod mewn ardaloedd / ardaloedd sy’n agos at y môr neu’r cefnfor, fel llywio gall offer llynges electronig fod yn destun cyrydiad / erydiad a all arwain at ocsidiad metel. Similarly, in microbiology laboratories and the medical industry, sensitive electronic equipment can be exposed to toxic chemicals, acidic and alkaline solvents that can accidentally spill onto a PCB, but the PCB’s “conformation coating” will protect the PCB and components from fatal injury.

Sut i gymhwyso cotio cydffurfiol?

In fact, the method of applying “conformal paint” in the right way is so important that careful consideration must be given to how conformal paint is applied. It is as important to choose suitable conformal coating materials.

Y prif ffactorau sy’n pennu cymhwysiad haenau cydffurfiol yn gywir yw:

1- Trwch paent

2- The level of coverage achieved

3- The degree of adhesion of paint to wood panels and their components.

There are five methods for applying conformal coatings:

1- Paent â llaw gyda brwsh

2- Gorchudd aerosol

3- Atomizing spray gun coating

4- Automatic dip coating

5- Automatic selection of coating

Dull halltu / sychu cotio cydffurfiol:

Conformal coatings themselves can be classified according to the drying and curing methods used after conformal coatings are completed. These methods are:

1- Heat/heat curing: Conformal coating is dried at high temperature. Drying rate is much faster than normal room temperature drying/curing.

2- halltu cyddwysiad: Mae gorchudd cydffurfiol PCB yn cael ei sychu ar dymheredd amgylchynol, mae lleithder yn yr atmosffer yn arafu’r broses halltu neu sychu.

3- ULTRAVIOLET (UV) curing: Here PCB with conformal coating is exposed to UV radiation. The uv energy determines the curing speed of PCB conformal coating

4- halltu ocsidiad: Yn y dull hwn, mae cynhyrchwyr PCB yn agored i amgylchedd awyr agored gyda llawer iawn o ocsigen atmosfferig, a fydd yn cynorthwyo i sychu / halltu cynhyrchwyr sy’n seiliedig ar doddydd

5- Catalytic curing: This is the process of curing conformal coating in which two materials are fused together, one of which is conformal coating. Ar ôl i’r cotio gael ei asio â deunyddiau catalydd eraill, ni ellir atal y broses halltu nes ei bod wedi’i chwblhau.

Classification of conformal coatings:

There are five main conformal coatings used: acrylic resin, epoxy resin, silicone, polyurethane (PU) and polyparaxylene coating.

L Resin acrylig (AAR):

Acrylics are ideal for (low-cost and high-volume) common electronics because AAR is inexpensive and can be easily applied to PCB surfaces by brush, dip, and manual or automatic spraying, reducing turnaround time and producing cost-effective products.

Budd-daliadau:

1 – cost isel

2- Easy for manual or automatic robot applications

3- Easy to rework

4- Excellent moisture protection

5- Good surface elasticity, can withstand static voltage discharge, and does not react with the atmosphere, therefore helps cure through solvent evaporation

Anfanteision:

1- Due to the use of atmospheric curing/drying methods for this material, proper ventilation systems need to be ensured

2- Cynnal a chadw gludedd isel

Gwrthiant gwisgo isel a gwrthiant cemegol

L Epoxy conformal coating (ER) :

Gellir cwblhau haenau cydffurfiol yn seiliedig ar resinau epocsi trwy frwsh llaw, chwistrell neu orchudd dip. Argymhellir chwistrellu ar gyfer cyfeintiau mwy ac ar gyfer PCBS cyfaint neu brototeip llai.

Budd-daliadau:

1- High moisture resistance and good dielectric resistance

2- Excellent chemical resistance, abrasion resistance, moisture resistance and high temperatures up to 150 O C

Anfanteision:

1-epoxy conformal paint is very hard and rigid and can damage PCB and its components if attempted peeling or removal. Tynnwch y cotio trwy ddefnyddio toddydd peryglus

2- Perfformiad tymheredd isel gwael

Crebachu halltu uchel

4- Mae’n anodd eu hail-wneud

L Gorchudd cydffurfiol resin silicon (OSR):

The softest of the above two types of conformal coatings is silicone resin (OSR) conformal coatings. They are widely used in LED lamp PCBS without reducing light intensity or color change. Ideal for PCB installation at high humidity and exposure to air. Suitable for PCB with high operating temperature and high power

Budd-daliadau:

1- Gwrthiant cemegol da, ymwrthedd lleithder, chwistrell halen a thymheredd uchel hyd at 200 OC

2- Good flexibility makes it resistant to vibration stress on PCB from external environment.

3- Yn addas ar gyfer cymwysiadau awyr agored PCB gyda lleithder uchel

Y drwg:

1- Peidio â gwrthsefyll gwisgo oherwydd priodweddau rwber

2- Gellir ei ail-weithio, ond nid yn hawdd, sy’n gofyn am doddyddion arbennig, amseroedd socian hir a’u troi fel brwsh neu faddon ultrasonic

3- Low mechanical strength, weak adhesion to PCB substrate

Gorchudd cydffurfiol L polywrethan (PU):

Yn addas ar gyfer cymwysiadau PCB ym maes modurol, diwydiannol, offeryniaeth a thelathrebu. Mewn awyrofod, yn benodol, mae anweddau tanwydd yn gwrthdaro’n gyson â’r prif gorff o offer electronig ac felly’n treiddio i’r tu mewn ac yn effeithio ar fwrdd y PCB

Budd-daliadau:

1- High resistance to moisture, chemicals (acid and alkali) and wear

Anfanteision:

1- Ar ôl amser hir o broses halltu gyflawn, mae’n tueddu i droi melyn ar dymheredd uchel oherwydd ei gynnwys VOC uchel

2- Fel silicon, nid yw’n hawdd ei dynnu’n llwyr

L polyparaxylene conformal coating:

This type of coating is suitable for avionics, microelectronics, sensors, high-frequency circuits, and densely populated PCB-based components. It is applied by means of vapor deposition.

Budd-daliadau:

1- Excellent dielectric strength

2- High resistance to moisture, solvents, extreme temperatures and acid corrosion

3- Can be applied evenly with very thin paint.

Anfanteision:

1- Mae dadosod / ailweithio yn anodd iawn

2- Cost uchel yw’r anfantais fwyaf.